XSERVER(1) X Version 11(Release 5) XSERVER(1)
NAME
Xserver - X Window System server
SYNOPSIS
X [:displaynumber] [-option ...] [ttyname]
DESCRIPTION
X is the generic name for the X Window System server. It is frequently a
link or a copy of the appropriate server binary for driving the most
frequently used server on a given machine.
STARTING THE SERVER
The server is usually started from the X Display Manager program xdm.
This utility is run from the system boot files and takes care of keeping
the server running, prompting for usernames and passwords, and starting
up the user sessions. It is easily configured for sites that wish to
provide nice, consistent interfaces for novice users (loading convenient
sets of resources, starting up a window manager, clock, and nice
selection of terminal emulator windows).
Installations that run more than one window system will still need to use
the xinit utility. However, xinit is to be considered a tool for
building startup scripts and is not intended for use by end users. Site
administrators are strongly urged to use xdm, or build other interfaces
for novice users.
When the X server starts up, it takes over the display. If you are
running on a workstation whose console is the display, you cannot log
into the console while the server is running.
NETWORK CONNECTIONS
The X server supports connections made using the following reliable
byte-streams:
TCP/IP
The server listens on port 6000+n, where n is the display number.
Unix Domain
The X server uses /tmp/.X11-unix/Xn as the filename for the socket,
where n is the display number.
DECnet
The server responds to connections to object X$Xn, where n is the
display number. This is not supported in all environments.
OPTIONS
All of the X servers accept the following command line options:
-a number
sets pointer acceleration (i.e. the ratio of how much is reported
to how much the user actually moved the pointer).
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-auth authorization-file
Specifies a file which contains a collection of authorization
records used to authenticate access. See also the xdm and
Xsecurity manual pages.
bc disables certain kinds of error checking, for bug compatibility
with previous releases (e.g., to work around bugs in R2 and R3
xterms and toolkits). Deprecated.
-bs disables backing store support on all screens.
-c turns off key-click.
c volume
sets key-click volume (allowable range: 0-100).
-cc class
sets the visual class for the root window of color screens. The
class numbers are as specified in the X protocol. Not obeyed by
all servers.
-co filename
sets name of RGB color database.
-dpi resolution
sets the resolution of the screen, in dots per inch. To be used
when the server cannot determine the screen size from the
hardware.
-f volume
sets feep (bell) volume (allowable range: 0-100).
-fc cursorFont
sets default cursor font.
-fn font
sets the default font.
-fp fontPath
sets the search path for fonts. This path is a comma separated
list of directories which the X server searches for font
databases.
-help prints a usage message.
-I causes all remaining command line arguments to be ignored.
-ld kilobytes
sets the data space limit of the server to the specified number
of kilobytes. A value of zero makes the data size as large as
possible. The default value of -1 leaves the data space limit
unchanged. This option is not available in all operating
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systems.
-lf files
sets the number-of-open-files limit of the server to the
specified number. A value is zero makes the limit as large as
possible. The default value of -1 leaves the limit unchanged.
This option is not available in all operating systems.
-ls kilobytes
sets the stack space limit of the server to the specified number
of kilobytes. A value of zero makes the stack size as large as
possible. The default value of -1 leaves the stack space limit
unchanged. This option is not available in all operating
systems.
-logo turns on the X Window System logo display in the screen-saver.
There is currently no way to change this from a client.
nologo turns off the X Window System logo display in the screen-saver.
There is currently no way to change this from a client.
-p minutes
sets screen-saver pattern cycle time in minutes.
-r turns off auto-repeat.
r turns on auto-repeat.
-s minutes
sets screen-saver timeout time in minutes.
-su disables save under support on all screens.
-t number
sets pointer acceleration threshold in pixels (i.e. after how
many pixels pointer acceleration should take effect).
-to seconds
sets default connection timeout in seconds.
ttyxx ignored, for servers started the ancient way (from init).
v sets video-off screen-saver preference.
-v sets video-on screen-saver preference.
-wm forces the default backing-store of all windows to be WhenMapped;
a cheap trick way of getting backing-store to apply to all
windows.
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-x extension
loads the specified extension at init. Not supported in most
implementations.
You can also have the X server connect to xdm using XDMCP. Although this
is not typically useful as it does not allow xdm to manage the server
process, it can be used to debug XDMCP implementations, and serves as a
sample implementation of the server side of XDMCP. For more information
on this protocol, see the X Display Manager Control Protocol
specification. The following options control the behavior of XDMCP.
-query host-name
Enable XDMCP and send Query packets to the specified host.
-broadcast
Enable XDMCP and broadcast BroadcastQuery packets to the network.
The first responding display manager will be chosen for the
session.
-indirect host-name
Enable XDMCP and send IndirectQuery packets to the specified
host.
-port port-num
Use an alternate port number for XDMCP packets. Must be
specified before any -query, -broadcast or -indirect options.
-once Normally, the server keeps starting sessions, one after the
other. This option makes the server exit after the first session
is over.
-class display-class
XDMCP has an additional display qualifier used in resource lookup
for display-specific options. This option sets that value, by
default it is "MIT-Unspecified" (not a very useful value).
-cookie xdm-auth-bits
When testing XDM-AUTHENTICATION-1, a private key is shared
between the server and the manager. This option sets the value
of that private data (not that it is very private, being on the
command line!).
-displayID display-id
Yet another XDMCP specific value, this one allows the display
manager to identify each display so that it can locate the shared
key.
Many servers also have device-specific command line options. See the
manual pages for the individual servers for more details.
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SECURITY
The X server implements a simplistic authorization protocol, MIT-MAGIC-
COOKIE-1 which uses data private to authorized clients and the server.
This is a rather trivial scheme; if the client passes authorization data
which is the same as the server has, it is allowed access. This scheme
is worse than the host-based access control mechanisms in environments
with unsecure networks as it allows any host to connect, given that it
has discovered the private key. But in many environments, this level of
security is better than the host-based scheme as it allows access control
per-user instead of per-host.
In addition, the server provides support for a DES-based authorization
scheme, XDM-AUTHORIZATION-1, which is more secure (given a secure key
distribution mechanism). This authorization scheme can be used in
conjunction with XDMCP's authentication scheme (XDM-AUTHENTICATION-1) or
in isolation.
The authorization data is passed to the server in a private file named
with the -auth command line option. Each time the server is about to
accept the first connection after a reset (or when the server is
starting), it reads this file. If this file contains any authorization
records, the local host is not automatically allowed access to the
server, and only clients which send one of the authorization records
contained in the file in the connection setup information will be allowed
access. See the Xau manual page for a description of the binary format
of this file. Maintenance of this file, and distribution of its contents
to remote sites for use there is left as an exercise for the reader.
The server also provides support for SUN-DES-1, using Sun's Secure RPC.
It involves encrypting data with the X server's public key. See the
Xsecurity manual page for more information.
The X server also uses a host-based access control list for deciding
whether or not to accept connections from clients on a particular
machine. If no other authorization mechanism is being used, this list
initially consists of the host on which the server is running as well as
any machines listed in the file /etc/Xn.hosts, where n is the display
number of the server. Each line of the file should contain either an
Internet hostname (e.g. expo.lcs.mit.edu) or a DECnet hostname in double
colon format (e.g. hydra::). There should be no leading or trailing
spaces on any lines. For example:
joesworkstation
corporate.company.com
star::
bigcpu::
Users can add or remove hosts from this list and enable or disable access
control using the xhost command from the same machine as the server.
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The X protocol intrinsically does not have any notion of window operation
permissions or place any restrictions on what a client can do; if a
program can connect to a display, it has full run of the screen. Sites
that have better authentication and authorization systems (such as
Kerberos) might wish to make use of the hooks in the libraries and the
server to provide additional security models.
SIGNALS
The X server attaches special meaning to the following signals:
SIGHUP This signal causes the server to close all existing connections,
free all resources, and restore all defaults. It is sent by the
display manager whenever the main user's main application
(usually an xterm or window manager) exits to force the server to
clean up and prepare for the next user.
SIGTERM This signal causes the server to exit cleanly.
SIGUSR1 This signal is used quite differently from either of the above.
When the server starts, it checks to see if it has inherited
SIGUSR1 as SIG_IGN instead of the usual SIG_DFL. In this case,
the server sends a SIGUSR1 to its parent process after it has set
up the various connection schemes. Xdm uses this feature to
recognize when connecting to the server is possible.
FONTS
Fonts are usually stored as individual files in directories. The X
server can obtain fonts from directories and/or from font servers. The
list of directories and font servers the X server uses when trying to
open a font is controlled by the font path. Although most sites will
choose to have the X server start up with the appropriate font path
(using the -fp option mentioned above), it can be overridden using the
xset program.
The default font path for the X server contains four directories:
/usr/lib/X11/fonts/misc
This directory contains many miscellaneous bitmap fonts that are
useful on all systems. It contains a family of fixed-width
fonts, a family of fixed-width fonts from Dale Schumacher,
several Kana fonts from Sony Corporation, two JIS Kanji fonts,
two Hangul fonts from Daewoo Electronics, two Hebrew fonts from
Joseph Friedman, the standard cursor font, two cursor fonts from
Digital Equipment Corporation, and cursor and glyph fonts from
Sun Microsystems. It also has various font name aliases for the
fonts, including fixed and variable.
/usr/lib/X11/fonts/Speedo
This directory contains outline fonts for Bitstream's Speedo
rasterizer. A single font face, in normal, bold, italic, and
bold italic, is provided, contributed by Bitstream, Inc.
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/usr/lib/X11/fonts/75dpi
This directory contains bitmap fonts contributed by Adobe
Systems, Inc., Digital Equipment Corporation, Bitstream, Inc.,
Bigelow and Holmes, and Sun Microsystems, Inc. for 75 dots per
inch displays. An integrated selection of sizes, styles, and
weights are provided for each family.
/usr/lib/X11/fonts/100dpi
This directory contains 100 dots per inch versions of some of the
fonts in the 75dpi directory.
Font databases are created by running the mkfontdir program in the
directory containing the compiled versions of the fonts (the .pcf files).
Whenever fonts are added to a directory, mkfontdir should be rerun so
that the server can find the new fonts. If mkfontdir is not run, the
server will not be able to find any fonts in the directory.
DIAGNOSTICS
Too numerous to list them all. If run from init(8), errors are typically
logged in the file /usr/adm/X*msgs,
FILES
/etc/X*.hosts Initial access control list
/usr/lib/X11/fonts/misc, /usr/lib/X11/fonts/75dpi, /usr/lib/X11/fonts/100dpi
Bitmap font directories
/usr/lib/X11/fonts/Speedo Outline font directories
/usr/lib/X11/fonts/PEX PEX font directories
/usr/lib/X11/rgb.txt Color database
/tmp/.X11-unix/X* Unix domain socket
/usr/adm/X*msgs Error log file
SEE ALSO
X(1), bdftopcf(1), mkfontdir(1), fs(1), xauth(1), xdm(1), xhost(1),
xinit(1), xset(1), xsetroot(1), xterm(1), Xdec(1), Xibm(1), XmacII(1),
Xmips(1), Xqdss(1), Xqvss(1), Xsun(1), Xtek(1), X386(1) X Window System
Protocol, Definition of the Porting Layer for the X v11 Sample Server,
Strategies for Porting the X v11 Sample Server, Godzilla's Guide to
Porting the X V11 Sample Server
BUGS
The option syntax is inconsistent with itself and xset(1).
The acceleration option should take a numerator and a denominator like
the protocol.
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If X dies before its clients, new clients won't be able to connect until
all existing connections have their TCP TIME_WAIT timers expire.
The color database is missing a large number of colors.
COPYRIGHT
Copyright 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991 Massachusetts
Institute of Technology.
See X(1) for a full statement of rights and permissions.
AUTHORS
The sample server was originally written by Susan Angebranndt, Raymond
Drewry, Philip Karlton, and Todd Newman, from Digital Equipment
Corporation, with support from a large cast. It has since been
extensively rewritten by Keith Packard and Bob Scheifler, from MIT.
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